The present invention relates to a power-assisted steering device for a vehicle, comprising control means acting upon steering means, said control means comprising a transmission element in two parts which parts are capable of limited relative angular displacement under the action of said control means, and power-assistance means which, in response to such angular displacement, act upon the steering means in the same sense as the control means. More particularly, the invention relates to such a device, in which the power-assistance means comprise a hydraulic unit having fluid-pressure means and a reservoir, an actuator acting upon the steering means, and a hydraulic distributor interposed between the hydraulic unit and the actuator.
The invention is concerned more specifically with a power-assisted device of this kind, in which the distributor comprises a stator which has a pressure orifice connected to the fluid-pressure means, a return orifice connected to the reservoir, and two service orifices connected to the actuator, and two adjacent rotors which are located within the stator and which rotate integrally with the two said parts of the transmission element respectively, a first of said rotors having distribution passages interacting with the pressure and return orifices of the stator, whilst the second rotor has distribution passages which interact both with the distribution passages of the first rotor and with the service orifices of the stator.
Generally in devices of this type, the fluid-pressure orifice feeds the pressure passages of the first rotor laterally. These passages occupy an intermediate position between the outer periphery and the inner periphery of the first rotor and feed some of the passages of the second rotor which feed the actuator, the return from which is effected via the other passages of the second rotor, then via channels which are formed on the outer periphery and on the inner periphery of the first rotor, whence the fluid returns to the reservoir or tank.
One known arrangement of this kind is generally satisfactory, but entails a considerable bulk both axially and radially, because the first rotor has passages both on its outer periphery and its inner periphery and in a region contained between these two peripheries.
The object of the present invention is a power-assisted steering device for a vehicle, of the kind described above, in which both the axial and the radial bulk of the device is reduced.